Abstract
Polyomavirus (PyV) is a circular double strand DNA virus with icosahedral capsid structure. Subtypes such as JC, and BK polyomavirus are known to infect human, most exclusively immunocompromised individuals with predilection of CNS or urinary system. More recently discovered strains including Merkel cell polyomavirus, HPyV6, HPyV7 and Trichodysplasia Spinuloa-Associated polyomavirus are known to affect human skin. Notably, HPyV6 and HPyV7 are associated with pruritus and continuous shedding in immunosuppressed individuals. Finding this feature in immunocompetent patient is yet to be reported. Herein, we report a case of seborrheic keratosis featuring unique histological characteristics of polyomavirus infection in an immunocompetent 68-year-old male, on a shave biopsy of right chest skin papule. The patient’s medical history includes of spinal stenosis, celiac artery aneurysm and squamous cell carcinoma of forehead. Microscopic examination showed mild acanthosis of the epidermis. Increased pigmentation was noted within keratinocytes of the basal layer of the lesion. The stratum granulosum and stratum corneum were marked by round to ovoid shape eosinophilic dyskeratotic materials, arranged in vertical fashion, known as “peacock plumage”, a unique cytopathic histomorphology of polyomavirus infection. Diagnosing PyV infection on skin is challenging. PCR is a mean of supportive diagnostic tool, yet, the negative result does not rule out the infection. Commercially used antibody against Large T-cell antigen of HPyV7 targets the viral protein needed for the viral replication. Hence, it has a low sensitivity in detecting cytopathic changes in anucleate stratum corneum. Differential of PyV infection should be considered when histopathological ‘peacock plumage’ sign is noted.